The complaint said Nichols’ excessive prescribing showed “a depraved mind” and a lack of regard for human life which led to the deaths of Debra Messner, Lynnette Nelson, Sheila Bartels, Chealsy Dockery, and Deborah Hutcheson.

The affidavit alleges that over a five year period, Nichols prescribed more than 1,800 opioid pills to the patients even though they didn’t need them. She prescribed three of the five patients a lethal combination of painkillers, muscle relaxants and anti-anxiety drugs.

“The dangers associated with opioid drugs have been well documented and most doctors follow strict guidelines when prescribing opioids to their patients. Nichols prescribed patients, who entrusted their well-being to her, a horrifyingly excessive amount of opioid medications,” said Hunter. “Nichols' blatant disregard for the lives of her patients is unconscionable.”

An investigation by the Oklahoma Bureau of Narcotics into Nichols began after a concerned former patient tipped off law enforcement that five patients had died of multi-drug toxicity. A state investigation found that Nichols prescribed more than 3 million doses of controlled dangerous drugs from 2010-2014.

After a September 2015 hearing before the Oklahoma State Board of Osteopathic Examiners, the board stripped Nichols of her prescribing authority of controlled dangerous substances. She voluntarily surrendered her credentials to the Drug Enforcement Administration and Oklahoma Bureau of Narcotics.

Messner died on March 30, 2010. She was prescribed Hydrocodone, Aplrazolam and Carisoprodol. An autopsy showed she died of "acute combined drug toxicity."

Nelson, 46, succumbed on March 1, 2012 as a result of combined drug toxicity a month after she was prescribed several controlled drugs by Nichols. A review of Nelson's file shows that in four years, Nichols had only conducted one full medical evaluation, in December 2008.

Bartels, 55, had a large prescription filled on November 21, 2012, after seeing Nichols. She died the same day of "multi-drug toxicity." A review of Bartels' file by a medical expert showed that she was prescribed an "irrational combination" of drugs, according to the affidavit.

Dockery, 21, died of combined drug toxicity on August 4, 2013 just three days after filling a prescription issued by Nichols.

On October 24, 2013, Hutcheson, 52, died of acute multi-drug toxicity. She was prescribed the drugs on October 8, 2013.

An Oklahoma County judge has issued a warrant for her arrest and will be held in lieu of $50,000 bond.

The murder charges against Dr. Nichols come as state officials embark on aggressive measures to tackle the opioid epidemic.

According to the US Centers for Disease Control and Prevention (CDC), more than 33,000 people died of opioid-related overdoses in the US in 2015, quadruple the rate in 1999. Opioids are the leading cause of overdose deaths in the US, with 91 Americans dying every day.

On Wednesday, the Missouri Attorney General became the third state to sue pharmaceutical companies for fraud. The civil lawsuit claims the firms carried out a complex, multi-year campaign in which they deliberately misrepresented the addictive risks of opioids, and “engaged in a deliberate campaign of fraud to convince Missouri doctors and consumers otherwise,” according to the complaint.

On June 16, Massachusetts Attorney General Maura Healey announced that her office has been working with a bipartisan coalition of state attorney generals to evaluate “whether [pharmaceutical] manufacturers used illegal practices in the marketing and sale of opioids and worsened this deadly crisis.”

In May, the Governor of Ohio, John Kasich, introduced new rules to limit doctors prescribing pain medications to seven days for adults, and no more than five days for minors.

The medications also can provide a gateway to heroin, according to the National Institute on Drug Abuse, which has reported that nearly half of young heroin users state that they had misused prescription opioids first.

Placing limits on doctors prescribing painkillers has already been adopted in other states. Massachusetts limits first-time painkiller prescriptions to 7 days. Other states that have passed laws with prescribing limits within the last year include Connecticut, Maine, New York, Rhode Island, and Vermont.